From 6d652c213da840dbdbc607b3a25ddf8020d0fe63 Mon Sep 17 00:00:00 2001
From: Andrei Bondarenko <andrei.i.bondarenko@gmail.com>
Date: Tue, 13 Jul 2021 19:49:20 +0200
Subject: [PATCH] Added Element dataclass

---
 core/element.py | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 core/element.py

diff --git a/core/element.py b/core/element.py
new file mode 100644
index 0000000..f428528
--- /dev/null
+++ b/core/element.py
@@ -0,0 +1,31 @@
+from dataclasses import dataclass, asdict, astuple
+from typing import TypeVar, Generic, Optional
+
+# Some typing information for Python static type checkers
+Literal = TypeVar('Literal', int, float, bool, str)  # Must be int, float, bool or str
+
+
+@dataclass
+class Element(Generic[Literal]):
+    """
+    An Element can represent one of following two things, based on the value of its attributes:
+
+    *   An element (node or edge) in the State (id is not None). In this case the value can be None because it hasn't
+        yet been read OR because the element doesn't have a value.
+    *   A value for which a node has not yet been materialized in the State (id is None, value is not None).
+
+
+    If you are familiar with the Modelverse Kernel, this class serves a function similar to the {id: ..., value: ...}
+    dict that is used there.
+    """
+    id: Optional[str] = None
+    value: Optional[Literal] = None
+
+    def is_none(self) -> bool:
+        return self.id is None and self.value is None
+
+
+String = Element[str]
+Integer = Element[int]
+Float = Element[float]
+Boolean = Element[bool]